You're porting an application to a newer (or older) Debian version, but the dependencies declared in the Debian package prevent it from being installed, and you don't want to make the package management unhappy.

First extract the files installed by the binary package:

$ dpkg-deb -x mypackage.deb mypackage

Next extract the package metadata:

$ dpkg-deb -e mypackage.deb mypackage/DEBIAN

At this point edit the control files in mypackage/DEBIAN. Finally, create the modified package: